If I understand your question correctly, there are

4 of 1 (a,b,c,d) 3+2+1=6 of 2 (ab,ac,ad,bc,bd,cd) 4 of 3 (abc,abd,acd,bcd) 1 of 4 (abcd)

I have no idea how you would make Excel display this, but I haven't tried. Login to read more.